Methods :
The CP-SSOCT sensor was fixed inside a 27-gauge needle, which was inserted into corneal stroma of an ex vivo bovine specimen. A high index epoxy lens was applied on the fiber sensor’s end to improve signal-to-noise ratio in corneal stroma and to protect the fiber’s end surface. A-scan images of the cornea were obtained at each step of insertion. A fiber sensor was fixed outside of cornea, 100um from the epithelium membrane, to determine whether both of epithelium and endothelium membranes can be identified at a large tilted angle without insertion of sensor into corneal stroma. A-scan images were obtained in 15° increments from 0° to 45°. The sensor position and angle were controlled by custom angular stage integrated with linear micro-motor needle drive.

Results :
The A-scan images in Figure 1 show position information of cornea layers during the insertion of the needle. Before insertion, the epithelium and endothelium membranes were identified, and after insertion, the needle approached the endothelium membrane as it was inserted deeper into stroma. Figure 2 shows A-scan images of bovine cornea obtained without insertion of sensor at various tilted angles. The position of the epithelium and endothelium membranes are still identifiable at 45°, which is acceptable angle for big bubble technique, although the peak intensity of endothelium layer decreased to 10% of peak intensity at 0°. The corneal thickness measured by the fiber sensor was 800um which is comparable to that measured by a reference based OCT imaging system.

Conclusions :
Our results are consistent with our hypothesis that CP-SSOCT fiber sensor can guide a needle insertion into corneal stroma for the big-bubble technique. It is expected that the endothelium membrane of human eyes is more easily identifiable, due to smaller corneal thickness of about 500um.

This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.